1. Field of the Invention
The present invention relates to an image forming apparatus, a printing operation control method and a computer-readable information recording medium that stores a computer program for carrying out a printing operation of forming an electrostatic latent image on a photosensitive member and fixing toner that adheres to the electrostatic latent image onto a recording medium.
2. Description of the Related Art
In a technical field of an image forming apparatus having a photosensitive member, it is known that, as a photosensitive member surface temperature increases, a state of the photosensitive member surface and/or image forming condition varies, which may result in degradation of an image formed in the image forming apparatus. An increase in the photosensitive member surface temperature may occur because of friction between the photosensitive member and a peripheral developing roller or transfer roller, friction heat caused by rotation of the roller, heat transmitted from a fixing device and so forth.
In the image forming apparatus, as the photosensitive member surface temperature becomes a predetermined temperature or more, the photosensitive member surface may be damaged. In the image forming apparatus, if the photosensitive member surface is damaged, the damaged part cannot be used for development. Therefore, an image output from the image forming apparatus has a blank corresponding to the damaged part, and thus, the image is defective.
In order to solve such a problem of an image defect caused by the photosensitive member surface temperature increase, the photosensitive member surface temperature is measured, and a printing operation in the image forming apparatus is continued or interrupted according to a thus-obtained temperature, for example.
FIG. 1 shows a state in which the photosensitive member surface temperature increases during a both-sides printing operation. A broken line in FIG. 1 shows a threshold for a temperature zone such that there is a high likelihood of occurrence of an image defect if the photosensitive member surface temperature becomes the threshold or more. In an example of FIG. 1, at a room temperature of 28° C. that is within an image compensation range, the photosensitive member surface temperature reaches the threshold (44° C.) when a printing operation is continued for approximately 55 minutes. In this case, such a control can be carried out that a printing operation is made to go on at a temperature of less than 44° C., and is interrupted at a temperature of 44° C. or more.
For example, according to Japanese Laid-Open Patent Applications Nos. 05-241405, 01-172853 and 58-116544, a photosensitive member surface temperature of a fixing temperature is measured, and printing is allowed according to a result of the measurement. By this method, it is possible to reflect the photosensitive member surface temperature in a printing operation, and it is possible to easily solve a problem of an image defect.
However, in order to realize the method, it is necessary to provide a sensor (temperature sensor) for measuring a temperature, which may result in a cost increase. Further, it is necessary to secure a space for disposing the temperature sensor. In conjunction with the space for disposing the temperature sensor, Japanese Laid-Open Patent Application No. 2003-043757 discusses the use of a measured temperature of another member that is in contact with the photosensitive member instead of directly measuring the photosensitive member surface temperature. Another method is to use a non-contact type temperature sensor (thermopile).